Scooters are well known in the art and generally include a platform with a forward wheel and a rear wheel, the forward wheel being generally pivotally mounted with a pair of handlebars for steering. In a variation on the standard well-known scooter, various types of drives have been adapted to the scooter with an extra wheel and drive axle added at the rear thereof in order to provide increased stability. In the prior art, one approach to driving these scooters with a mechanical drive teaches the use of a pair of reciprocating treadles, each of which has an end thereof pivotally secured in a fixed position while the other end oscillates in some manner, generally up and down, to drive a crank axle or the like. In some prior art devices, ratchet mechanisms are used to ensure that the vehicle is driven in only the forward direction. One other prior art device eliminates the generally fixed pivotal mounting of the treadle ends and instead mounts those treadle ends with a second, non-functional, crank arm arrangement such that the treadles maintain their generally horizontal orientation to a much greater extent as the treadles are reciprocated.
While these various designs have been met with some success in the prior art, virtually all, if not all, of these designs suffer from a simplistic drive train which does not adequately deal with the problem of a "dead spot" which is inherently found therein. Typically this "dead spot" exists when one treadle is at the beginning of its stroke while the other treadle is at the end of its stroke. As each treadle typically powers the drive axle or the like through an arc of only 180.degree., at this balanced point there is a significantly reduced (or even non-existent) torque which can be applied by the rider. Presumably, the designers of these prior art devices relied on the inertia of the rider and scooter to "glide" through this "dead spot". To start from this orientation, the rider pushes the vehicle with his leg to escape this "dead spot". Thus, prior art vehicles generally ignore this "dead spot" as it may be accommodated for. However, this "dead spot" does interfere with the continuous propelling of such a vehicle in that it creates a less than smooth transition from one treadle to the other as the rider shifts his weight to continue propelling the scooter. This undoubtedly creates more interference at slower speeds than at faster speeds, but these slower speeds are generally those most often used by a child with a scooter-type device.
In order to solve these and other problems in the prior art, the inventors herein have succeeded in designing and developing a treadle drive for a scooter which utilizes a unique track and roller mechanism for achieving a driving relationship between each treadle and a crank axle through an arc substantially greater than 180.degree., and even approaching 270.degree.. Thus, the "dead spot" of the prior art drives is eliminated. This is achieved by a bar-type track which supports a roller secured to the forward end of each treadle, the bar-type track having a generally flattened or horizontal portion thereof at its forward end and an inclined portion extending rearwardly. The rear end cf each treadle is secured to the opposing cranks in a crank axle. As the treadle is reciprocated the forward end of the treadle reaches the flat portion of the track and is supported therefrom by its roller so that torque is generated by a pivoting action thereabout. This pivoting action forces the rearward end of the treadle to drive the crank axle downwardly (as the vehicle is propelled in the forward direction). The treadle then moves off this flattened portion and onto the backward inclined portion such that continued downward movement of the treadle drives the crank axle past its six o'clock position by the weight of the rider. With this arrangement, as the treadles are reciprocated, each treadle thus drives its associated crank from a position just past its twelve o'clock orientation to a position near its nine o'clock position. As each treadle remains in a driving relationship with the crank axle through greater than 180.degree., there is an overlap between the treadles and a smooth transition between treadles results. Furthermore, there is no "dead spot", as in the prior art, as at least one treadle is always in drawing relationship with the crank axle.
The treadle drive of the present invention also permits driving the scooter in a reverse direction by merely changing the weight shifting from that required to drive it in the forward direction. As in the forward direction, the treadle drive achieves a driving relationship between the treadle and the crank axle through an arc much greater than 180.degree.. This driving action is achieved for the same reasons as mentioned above in connection with driving the scooter in the forward direction.
As can be appreciated, one of the goals of a scooter-type vehicle is to provide a smooth driving arrangement so that propelling the scooter can be achieved by even the littlest of children. Furthermore, reduced complexity is required in order to price the scooter reasonably for sale as a toy-type device. This places limits on the complexity of the drive mechanism. With the present invention, the smallest of children are capable of driving the scooter in either the forward or reverse direction and as the treadles remain generally horizontal as they are reciprocated, children are able to easily maintain their balance on the scooter as they propel it. In use, the inventors have found that after a short learning period, most children are capable of readily reciprocating the treadles to propel the scooter in both directions and are capable of doing so at slower speeds as well as faster speeds. As explained above, slower speeds with the present invention are accommodated through the ability of the treadle drive to power the crank axle through an arc greater than 180.degree..
While the principal advantages and features of the present invention have been discussed above, a greater understanding thereof may be attained by referring to the drawings and description of the preferred embodiment which follow.